Which master cylinder bore size to use for power disc Kelsey/Hayes

The stock bore is 1"

This master is only 0.03125" larger in diameter.

.835 sq in

.785 sq in

It's only 6% more force.

If you press with 250 lbs of force you add 15 extra pounds. Negligible.


Not to mention, I bet all 1 inch mc that have been rebuilt once or twice are close to that size

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Yeah over the decades I ran the stock size bore and some I bought prob bigger bore. Now I run a 15/16 bore with EBC reds, steel braided flex lines, 7/8 rear cylinders. If other ppl like using two feet to stop, 6 percent more force or what ever, go ahead put what ever you want on your car don't matter to me.